Joint structure of electric wire, stator of rotary electric machine, method for manufacturing the same

ABSTRACT

When electric wires (joint conductors) are disposed adjacent each other in a peeled state of coatings, a gap corresponding to the total thickness of both conductors&#39; insulating films as skin layers is formed between end joined face portions of the conductors. The gap becomes larger because the conductors are tapered. Therefore, the adhesion between both conductors is impaired, with a consequent fear of occurrence of joining imperfection. In opposed joined face portions of electric wires (joint conductors), the conductors are deformed from the tips of their axes to the joined face side in such a manner that exposed portions at the tips of the conductors and insulating film faces located in the vicinity thereof are flush with each other or the exposed portions are projected. The gap formed between the electric wires (joint conductors) can be diminished, whereby the reliability of connection is improved and it becomes easier to perform the work of joint conductors, with the result that the productivity of a stator of a rotary electric machine such as an AC generator for a vehicle could be improved.

CLAIM OF PRIORITY

The present application claim priority from Japanese application serialNo. 2005-150316, filed on May 24, 2005, the content of which is herebyincorporated by reference into this application.

FIELD OF THE INVENTION

The present invention relates to a stator of a rotary electric machinesuch as, for example, an AC generator for a vehicle and a method formanufacturing the same, as well as a joint structure of electric wiresand a method for manufacturing the same.

BACKGROUND OF THE INVENTION

According to a known electric wire, an end portion of an electric wire(a joint conductor) which end portion extends over a predetermined rangefrom a tip of the wire is plastically deformed so that a sectional areathereof becomes smaller than that of a main portion of the conductor,and the wire is constructed so that the main portion and a part of theend portion near the main portion are coated uniformly with aninsulating film, then two such electric wires (joint conductors) arejoined together in a matched state of respective end portions.

[Patent Literature 1]

Japanese Patent Laid-Open Publication No. 2002-95198

In the above conventional technique, since the sectional area of the endportion is decreased while preventing damage of the insulating film, aheat input quantity can be decreased. Consequently, there is no fearthat an insulating material located near a joined portion may bedeteriorated with heat produced a joining work, and hence the insulatingperformance is not impaired.

In the above conventional technique, however, if two electric wires(joint conductors) are positioned adjacent each other in a peeled stateof respective insulating coatings, there is formed a gap withcorresponding to the total thickness of both conductor's insulatingcoatings as skin layers in a joined face portion between end portions ofthe conductors. The gap becomes larger because the conductors aretapered at their tips. Therefore, the adhesion between both conductorsis impaired, with a consequent fear of occurrence of joiningimperfection.

It is an object of the present invention to minimize the gap developedbetween electric wires (joint conductors), thereby improving thereliability of joining, and facilitate the conductor joining work,thereby improving the productivity of a state of a rotary electricmachine such as, for example, an AC generator for a vehicle.

SUMMARY OF THE INVENTION

The present invention provides an electric wire joint structurecomprising:

insulator-coated wires each having a portion where an insulator coatingis removed to expose the conductor, wherein exposed portions of theconductors are opposed to each other to form joining faces; the joiningfaces of the exposed portions being flush with the surfaces of theinsulator coatings of the insulator-coated wires or being projected fromthe surfaces of the insulator coatings of the insulator-coated wires,and the joining faces being metallurgically joined.

According to one aspect of the present invention, for achieving theabove-mentioned object, in opposed joined face portions of electricwires (joint conductors), the axes of the conductors' exposed portionsare offset relative to the axes of the insulating coating in such amanner that exposed tip portions of the conductors and insulatingcoating faces located in the vicinity thereof are flush with each otheror the conductors' exposed portions are projected.

According to another aspect of the present invention constructed asabove, since joined faces of the joined face portions at the tips of theconductors with insulating coatings removed confront each other, it isnot necessary to keep the two pushed against each other with a strongforce during the joining work. Besides, it is possible to diminish thelikelihood of peeling-off of the joined face portion caused byspring-back after joining. As a result, not only the rationalization ofthe joining work can be attained, but also the reliability of the joinedstate of the joined face portion is improved and so are the productivityand reliability of, for example, the stator of a rotary electricmachine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged perspective view showing a connection betweenelectric wires (joint conductors) to which the present invention isapplied;

FIG. 2 is a diagram illustrating a process of cutting joined faceportions into a shape easy to weld;

FIG. 3 is a diagram showing a welded state of the joined face portions;

FIG. 4 is a diagram for explaining in what state the joined faceportions are Tig-welded;

FIG. 5 is a diagram showing a process of chipping off enamel coatings onshort sides;

FIG. 6 is a diagram showing a process of chipping off enamel coatings onlong sides;

FIG. 7 is an enlarged diagram of a circular frame portion in FIG. 5;

FIG. 8 is an enlarged diagram of a circular frame portion in FIG. 6;

FIG. 9 is an appearance diagram of a chip-off device;

FIGS. 10A to 10D are diagrams for explaining a process of chipping offenamel coatings on shorts sides;

FIG. 11 is a perspective view showing insulated conductors afterchipping-off of the short-side enamel coatings;

FIGS. 12A to 12F are diagrams for explaining a process of chipping offenamel coatings on long sides;

FIG. 13 is a perspective view showing the insulated conductors afterchipping-off of the short- and long-side enamel coatings;

FIG. 14 is a diagram showing a state in which the insulated conductorsafter chipping-off of the short- and long-side enamel coatings have beenset to a cutting device;

FIG. 15 is a diagram for explaining another machining method;

FIG. 16 is a diagram showing base metals of coil conductors used in astator of a rotary electric machine;

FIG. 17 is a diagram showing bent coil conductors;

FIG. 18 is a diagram showing an inner coil and an outer coil each formedin the hexagonal shape;

FIG. 19 is a diagram showing a part of a stator of a rotary electricmachine according to the present invention;

FIG. 20 is a diagram for explaining a process to be carried out prior toa stator assembling process;

FIG. 21 is a diagram for explaining another process to be carried outprior to the stator assembling process;

FIG. 22 is a diagram for explaining a state in which a stator core hasbeen set to a stator assembling fixture;

FIG. 23 is a diagram for explaining in which state inner coils are setto the stator core;

FIG. 24 is a diagram for explaining in which state outer coils are setto the stator core;

FIG. 25 is a diagram showing the stator core with inner and outer coilsset thereto;

FIG. 26 is a diagram for explaining a process of twisting the outercoils;

FIG. 27 is a diagram for explaining a process of deforming and caulkingthe outer coils into a state necessary for joining;

FIG. 28 is a diagram for explaining a process of welding joined faceportions of the outer coils;

FIG. 29 is a diagram for explaining a process of twisting the innercoils;

FIG. 30 is a diagram for explaining a process of deforming and caulkingthe inner coils into a state necessary for joining; and

FIG. 31 is a diagram for explaining a process of welding joined faceportions of the inner coils.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described hereinunder withreference to the drawings.

FIG. 1 is an enlarged perspective view showing a connection betweenelectric wires (joint conductors) to which the present invention isapplied.

Electric wires (joint conductors) 1 and 2 respectively compriseconductors 1A and 2A of a rectangular section coated and insulated withenamel coatings 1B and 2B.

The enamel coatings 1B and 2B are chipped off at tips of the electricwires (joint conductors) 1 and 2 to form, at the tips, projectingportions 1C and 2C which are the smallest in sectional area. The smallprojecting portions 1C and 2C function as cutting portions when cuttinga single long conductor (a detailed description will be given later) toform a conductor piece of a required length. Sectional area portions ofa medium size, which function as welding portions 1D and 2D, are formedbetween the small projecting portions 1C, 2C and the enamel coatings 1B,2B. One sides between the small projecting portions 1C, 2C and thewelding portions 1D, 2D are connected together through first slant faces1E and 2E having outward inclinations toward the enamel coatings 1B and2B.

The welding face portions 1D, 2D and the enamel coatings 1B, 2B(portions of the largest sectional area) are connected together throughstepped portions 1F and 2F.

Further, second slant faces 1G and 2G having outward inclinations towardthe enamel coatings 1B and 2B are formed between the stepped portions1F, 2F and the enamel coatings 1B, 2B.

The sides of the electric wires (joint conductors) 1 and 2 opposite tothe side including the first slant faces 1E, 2E, and the steppedportions 1F, 2F are formed flat from the enamel coatings 1B and 2B up totips of the small projecting portions 1C and 2C.

At the flat face portions, indicated at 1H and 2H, the tip portions ofthe joint conductors 1 and 2 are in close contact with each other.

This construction is characteristic in that there is no gap betweenjoined faces formed by the flat face portions-1H and 2H. As a result,the heat dissipating area of the joined face portions diminishes byabout 25% and it becomes possible to effect joining to a satisfactoryextent with a relatively small quantity of heat during welding. Coupledwith a reduced quantity of heat because of a small sectional area of thetip portions of the conductors, it becomes possible to conduct heatingmore effectively.

The remaining two faces at the tips of the electric wires (jointconductors) 1 and 2 are formed as flat faces 1J, 2J and flat faces (notshown) on the back sides.

Also on the flat faces 1J and 2J the enamel coatings 1B and 2B arechipped off to form third slant faces 1 k and 2K which are inclinedoutwards toward the enamel coatings 1B and 2B. This is also true of theback faces.

The first slant faces 1E, 2E, the second slant faces 1G, 2G, the thirdslant faces 1K, 2K, the flat faces 1J, 2J and their back faces areformed with edges of a cutter (to be described later) which chips offthe coatings 1B and 2B of the conductors.

FIG. 2 is a diagram explanatory of a process of cutting the joined faceportions into a shape which facilitates welding.

Before welding, the tip portions of the electric wires (jointconductors) 1 and 2 are cut by operating cutting edges 20A and 20B of acutter 20 in the directions of arrows in FIG. 2 at intermediatepositions (shown in FIG. 2) of the welding face portions 1D and 2D asportions of a medium sectional area.

FIG. 3 shows a welded state of both conductors by Tig welding (TungstenInert Gas welding) on the cut faces.

FIG. 4 illustrates in what manner the joined face portions areTig-welded.

By welding the cut faces, indicated at 1L and 2L, by Tig welding(Tungsten Inert Gas welding), the joined faces of the electric wires(joint conductors) 1A and 2A are joined together by molten metal 30.

More specifically, a heat-resistant tungsten electrode 42 is held in acollet 41 of a torch 40 and an inert gas (argon or helium gas) 44 isintroduced through a gas introducing pipe 43 around the tungstenelectrode 42 and is ejected through a gas nozzle 47 to around a weldingportion. A jet 48 of the inert gas cuts off the welding portion fromair, creating an oxygen-free state. As a result, the material isdifficult to be oxidized because there is no oxygen (air) in the weldingportion. Since the electric wires (joint conductors) 1A and 2A arecopper wires, they are used as positive electrodes, while an electrode41A of the collet 41 is used as a negative electrode, and a DC voltageis applied, causing an arc 40B to be produced between the tungstenelectrode 42 and the joined faces 1L, 2L of the electric wires (jointconductors) 1A, 2A. In this welding, the temperature of the arc 40Breaches a temperature of 5000 to 30000 degrees. With the heat of the arc40B, the joined face portion between the joined faces 1L and 2L ismelted and welded.

The smaller the heat dissipating area and the smaller the amount of heatdissipated, the earlier the temperature of the welding portion can beraised up to the metal melting temperature.

Besides, since there is no gap between the joined faces, there is nosump of air (oxygen), and even if a negative pressure portion occurs inthe welding portion by the flow of inert gas which is blown off againstthe welding portion, there is no fear of air (oxygen) being introduced(flowing reverse) into the joined face portion and the welding portionis so much difficult to be oxidized, because in the welding portionthere is not such a gap as serves as an air introducing passage.

Since the joined faces are in close contact with each other, it is notnecessary push the joined faces with a strong force from the exteriorduring welding. The problem that the joined portion springs back (aphenomenon that the joined portion repulses the pushing force and tendsto revert to the original separated state) after welding, causingseparation of the welded portion, is also solved. Further, it is notnecessary to retain the pushing force until the joined portion gets coldfor the prevention of separation caused by such a spring-backphenomenon, and the time required for the joining can so much beshortened.

When the electric wires (joint conductors) are joined in a stand-upstate, the stepped portions 1F and 2F act as receiving portions ofmolten metal spatter, whereby the possibility of the spatter adhering tofor example of the face of the insulating film and impairing theinsulating property can also be diminished.

Now, with reference to FIGS. 5 and 6, a description will be given belowabout a method and apparatus for manufacturing the electric wires (jointconductors) 1 and 2 described above.

As also described earlier, the electric wires (joint conductors) 1 and 2according to this embodiment are rectangular conductors whose sectionperpendicular to the longitudinal axis of each conductor is arectangular section comprising long and short sides. The outerperipheries of the electric wires are coated for insulation with enamelcoatings 1A and 2A.

In case of welding an end portion of a conductor to another conductor,the enamel coating thereof becomes an obstacle. Therefore, it isnecessary to remove the enamel coating on the end portion of eachconductor which portion serves as a conductor joined face portion tofacilitate welding. Besides, the machining method should be a methodsuitable for automation so that the enamel coating removing work and acutting work for cutting the conductor into a specific length suitablefor the purpose of use.

FIGS. 5 to 12 are drawings for explaining the enamel coating removingwork, of which FIG. 5 illustrates a process of chipping off the enamelcoatings on short sides, FIG. 6 illustrates a process of chipping offthe enamel coatings on long sides, FIG. 7 is an enlarged diagram of acircular frame portion in FIG. 5, FIG. 8 is an enlarged diagram of acircular frame portion in FIG. 6, and FIG. 9 is an appearance diagram ofa chip-off device.

Chip-off devices 50 and 60 comprise fixed dies 51, 61 and movable dies52, 62.

The fixed dies 51 and 61 comprise a pair of fixed clamping fixtures 51A,51B and a pair of fixed clamping fixtures 61A, 61B, respectively, andcentrally provided, combined conductor guides and fixed blades 51C and61C, respectively.

The movable dies 52 and 62 comprise a pair of movable cutting blades52A, 52B and a pair of movable cutting blades 62A, 62B, respectively,and centrally provided, conductor pressers 52C and 62C, respectively.

The combined conductor guides and fixed cutting blades 51C, 61C and themovables cutting blades 52A, 52B, 62A, 62B have respective edges 51 a,51 b, 61 a, 61 b, 52 a, 52 b, 62 a, and 62 b.

The chip-off devices 50 and 60 are installed side by side before andafter a machining line. An enamel coating 100A on each short side isfirst excised and this excised portion is fed to the position of thechip-off device 60, where the enamel coating 100A on each long side ischipped off. In this way enamel coating 100A-chipped off portions areformed continuously at certain intervals on the long conductor.

As shown in FIG. 9, at an inlet and an outlet of the chip-off device 50there are provided conductor feed guides 101 and 102, respectively, forfeeding straight an insulated conductor. An insulated conductor 100which has been fed over a certain length by means of a feeder (notshown) is guided into a groove 51F in such a manner that long sides ofthe conductor 100 come into abutment against the slot, the groove 51F(FIG. 7) being formed in an end face of the combined conductor guide andfixed cutting blade SiC in the chip-off device 50.

As shown in FIGS. 5, 7 and 10, the insulated conductor 100 is presseddown in the direction of the combined conductor guide and fixed cuttingblade 51C by means of the conductor presser 52C which is disposed at aposition confronting the combined conductor guide and fixed cuttingblade 51C, whereby the position of the insulated conductor 100 is fixed(see FIGS. 10A and 10C).

Next, the movable blades 52A and 52B move from above to below in thedrawings, with the result that a shear force is developed between theedges 52 a, 52 b of the movable cutting blades 52A, 52B and the edges 51a, 51 b of the combined conductor guide and fixed cutting blade 51C. Thedrawings illustrate a state in which the coating is being chipped offwith the shear force. The chipped-off coating and a part of theconductor (chips resulting from cutting) are held in gaps 51D and 51Eformed between the fixed clamping fixtures 51A, 51B and the combinedconductor guide and fixed cutting blade 51C (see FIGS. 10B and 10D).

When the chipping-off of the enamel coating 100A on short sides is over,the insulated conductor 100 is fed to the position of the next chip-offdevice 60 by means of a feeder (not shown).

FIG. 11 shows an appearance of the insulated conductor upon completionof chipping-off of the short-side enamel coating 100A. The sameconstituent portions as in FIG. 1 are identified by the same referencenumerals as in FIG. 11.

The chip-off device 60 is disposed at a position corresponding to a90°-rotated position of the chip-off device 50. The movable cuttingblades 62A and 62B of the chip-off device 60 are disposed on the samemachining line so as to reciprocate perpendicularly to the movablecutting blades 52A and 52B of the chip-off device 50.

Like the device shown in FIG. 9, the chip-off device 60 is also providedwith conductor feed guides 101 and 102 at an inlet and an outlet,respectively, for feeding the insulated conductor straight. The enamelcoating 100A-chipped off portion on a short side of the insulatedconductor 100 which has been fed a certain length by the feeder (notshown) is set to the position of a groove 61F which is formed in an endface of the combined conductor guide and fixed cutting blade 61C of thechip-off device 60. In this state a gap is still present between theface of the chipped-off portion and the face of the groove 61F (seeFIGS. 12A and 12D).

FIGS. 6 and 8 show an interim state. Before reaching the state shown inFIGS. 6 and 8, first the movable blades 62A and 62B move from right toleft in the figures, with the result that the edges 62 a and 62 b of themovable cutting blades 62A and 62B come into abutment against theto-be-chipped off portion of the insulated conductor 100. As shown inFIGS. 12B and 12E, the edges 62 a and 62 b of the movable cutting blades62A and 62B are formed axially longer than the edges 52 a and 52 b ofthe movable cutting blades 52A and 52B, so that the insulated conductorcan be chipped off over a longer axial portion than the portion whichhas been cut with the edges 52 a and 52 b of the movable cutting blades52A and 52B in the previous process. Consequently, it is possible tosolve the problem that the conductor is torn off in the portion of asmall sectional area previously chipped off when the edges 62 a and 62 bof the movable cutting blades 62A and 62B come into abutment againstonly the said potion of a small sectional area.

Further, as the edges 62 a and 62 b of the movable cutting blades 62Aand 62 b move toward the combined conductor guide and fixed cuttingblade 61C, the long-side portions with the sectional area not reducedyet begin to be chipped off by the edges 62 a and 62 b. At this time,the pressing force of the movable cutting blades 62A and 62B is borne byabutment of an outer face of the axially outer portion of a largersectional area with respect to the portion chipped off previously by theedges 52 a and 52 b of the movable cutting blades 52A and 52B againstthe fixed clamping fixtures 61A and 61B (see FIGS. 12B and 12E).

Then, as the edges 62 a and 62 b move toward the combined conductorguide and fixed cutting blade 61C, the edges 62 a and 62 b reach theface of the portion of a smaller sectional area which was chipped offwith the edges 52 a and 52 b of the movable cutting blades 52A and 52Bin the previous process. At this time, the portion chipped off in theprevious process and reduced in sectional area undergoes the pressingforce of the conductor presser 62C and that of the movable cuttingblades 62A, 62B and is deformed leftwards in the drawings. Thisdeformation continues until the groove 61F-side face of the portionreduced in sectional area is pressed against the bottom face of thegroove 61F (see FIGS. 12C and 12F).

After abutment of the groove 61F-side face of the portion reduced insectional area against the bottom face of the groove 61F, the conductoris excised with a shear force developed between the edges 62 a, 62 b ofthe movable cutting blades 62A, 62B and the edges 61 a, 61 b of thecombined conductor guide and fixed cutting blade 61C.

FIGS. 6 and 8 show an interim state, in which the chipped-off coating100A and a part of the conductor (chips resulting from cutting) are heldin gaps 61D and 61E formed between the fixed clamping fixtures 61A, 61Band the combined conductor guide and fixed cutting blade 61C.

In FIG. 9, the fixed and movable dies 51, 52 and cutting blades arepositioned by positioning pins 56A and 56B.

FIG. 13 shows the insulated conductor 100 after chipping-off of theshort- and long-side enamel coatings. The reference numerals describedin FIG. 13 are the same as those used for the electric wires (jointconductors) 1 and 2 in FIG. 1, indicating the same portions as in FIG.1.

After the enamel coatings have been chipped off by the excising devices50 and 60, the pair of electric wires (joint conductors) 1 and 2 assumea state in which both are connected together through the projectingportion 1C.

The portion of the smallest sectional area is formed by central edgeportions of the edges 52 a and 52 b of the movable cutting blades 52Aand 52B when the short-side coating is chipped off. In FIG. 13, the sizeof a short side is L1 and that of a long side is L2, both being in therelation of L1<L2.

A cutting device is disposed at a position just behind the chip-offdevice 60 on the machining line. When the chipping-off is completed bythe chip-off device 60, the electric wires are fed up to the position ofthe cutting device.

FIG. 14 is a sectional view taken along line P-P in FIG. 13, showing astate in which the insulated conductors are set to the cutting device.

As shown in FIG. 14, the cutting device includes a cutting blade 110 andcut assisting fixtures 111 disposed on both sides of the cutting blade110. The cut assisting fixtures 111 function not only as guides for thecutting blade 110 but also as holding fixtures for holding theconductors firmly. In a state in which the conductors are pressedagainst a receiving die 112 by the cut assisting clamping fixtures 111,the cutting blade 110 is moved toward the receiving die 112, whereby theportion of the smallest section is cut to form a projecting portion 1C.

At this time, the faces of the electric wires (joint conductors) 1 and 2which faces are in contact with the receiving die 112 form joined faces1H and 2H after the cutting. As shown clearly in FIG. 14, the joinedfaces 1H and 2H are deformed (offset to one side from the center) so asto be flush (coplanar) with the faces of the enamel coatings 1B and 2B.

Although in the above embodiment the enamel coating-chipped off portionsare thus deformed (offset to one side from the center) simultaneouslywith the chipping-off of the long-side enamel coating, there may beadopted a method wherein the portions in question are not deformed(offset to one side from the center), but are pressed and deformedlongitudinally as indicated with broken lines by pressing fixtures 113and 114 in the cutting process, as shown in FIG. 15, followed by cuttingof the portion of the smallest section with use of the cutting blade110.

FIG. 16 illustrates coil conductors in a stator of a rotary electricmachine which is provided with the electric wires (joint conductors)shown in FIGS. 1, 13 and 14.

The coil conductors, which constitute a stator in the rotary electricmachine, are an inner coil 131 inserted inside a slot of the stator, anouter coil 133 inserted outside the slot, and a crossover coil 132 whichprovides a connection between the inner and outer coils.

Enamel coating-chipped off portions 131A, 131B, 132A, 132B, 133A, and133B of the shape described above are formed at both ends of the coilconductors by the above process.

Each coil conductor is bent nearly centrally, as shown in FIG. 17. Adescription on the bending process will be described later.

As shown in FIG. 18, the inner and outer coils 131, 133 are each formedin a generally hexagonal shape. Twisted portions 131C, 133C and slantside portions 131G, 131F, 133G, 133F form crossover line portions ofstator coils.

In the enamel coating-chipped off portions 131A, 131B, 133A, and 133B,predetermined joined face portions are joined together at their joinedfaces, then are cut as in FIG. 2, and thereafter welded as in FIGS. 3and 4.

The coils thus formed are inserted into slots 161 of the statorindicated at 160, as shown in FIG. 19 and are joined by welding in therespective joined face portions to form stator coils.

Next, a process of forming the stator coils 131, 133 and a process ofassembling the stator 160 will be described below with reference toFIGS. 20 to 31.

The coil conductors shown in FIG. 16 which serve as base metals of theinner and outer coils 131, 133 are formed in U shape in a U shapeforming process (not shown), then in the process shown in FIG. 20,plural U-shaped inner and outer coils 131, 133 are inserted and set intoseparate inserting fixtures 200.

In the process shown in FIG. 21, the U-shaped portions of the pluralinner and outer coils 131, 133 set in the inserting fixtures 200 aretwisted by twisting fixtures 210.

In the process shown in FIG. 22, a stator core 302 is set in a statorassembly fixture 300 provided with a coil guide 301.

In the process shown in FIG. 23, the inner coils 131 are first set usingthe coil guide 301 into slots formed in the stator core 302 which hasbeen set in the stator assembling fixture 300.

In the process shown in FIG. 24, the outer coils 133 are inserted andset into slots formed in the stator core 302 with use of the coil guide301 so as to be positioned outside the inner coils 131 which havealready been set.

FIG. 25 shows the stator core 302 with inner and outer coils 131, 133set therein.

In this state, joined end portions of the inner and outer coils 131, 133are not ready for joining yet.

In the process shown in FIG. 26, the outer coils 133 are first pushedinto the stator 302 with use of a coil pushing jig 303 and a rotaryshaft 304 is rotated in e direction of arrow, causing a lower die 305 torotate and thereby twisting the joining end portions into apredetermined shape.

In the process shown in FIG. 27, the lower die 305 is removed andterminals of the outer coils 133 are deformed into a state necessary forjoining as in FIG. 1, followed by caulking to effect forming.Thereafter, cutting is performed by the cutting device as in FIG. 2 andpreparations are made for welding.

In the process shown in FIG. 28, the joined face portions are welded byTig welding by the method shown in FIGS. 3 and 4. At this time, awelding height is measured by a sensor 306 and a check is made to seewhether the measured height is an appropriate height or not.

In the process shown in FIG. 29, the inner coils 131 are pushed into thestator 302 with use of a coil pushing jig 307 and the rotary shaft 304is rotated in the direction of arrow to rotate the lower die 305,thereby twisting the joining end portions into a predetermined shape.

In the process shown in FIG. 30, the lower die 305 is removed andterminals of the inner coils 131 are deformed into a state necessary forjoining as in FIG. 1, followed by caulking to effect forming.Thereafter, cutting is performed by the cutting device as in FIG. 2 andpreparations are made for welding.

In the process shown in FIG. 31, the joined face portions are welded byTig welding by the method shown in FIGS. 3 and 4. At this time, awelding height is measured by the sensor 306 and a check is made to seewhether the measured height is an appropriate height or not.

In this way the stator shown in FIG. 19 is obtained.

1. An electric wire joint structure comprising: insulator-coated wires,each having an insulator coated portion, and a portion where aninsulator coating is removed to expose a conductor; wherein exposedportions of the conductors are opposed to each other and form joiningfaces; said joining face of each respective insulator-coated wire isflush with a surface of the insulator coating of that respectiveinsulator-coated wire; and the joining faces are metallurgically joinedto form a joined face portion.
 2. The electric wire joint structureaccording to claim 1, wherein a sectional area of each conductor in thejoined face portion is smaller than a sectional area of theinsulator-coated portion.
 3. The electric wire joint structure accordingto claim 1, wherein a surface of each conductor in the joined faceportion, opposite the joining face, comprises a slant face.
 4. Theelectric wire joint structure according to claim 1, wherein, in thejoined face portion, each conductor has a rectangular section.
 5. Theelectric wire joint structure according to claim 1, wherein, in theinsulator-coated portion, each conductor has a rectangular section. 6.The electric wire joint structure according to claim 1, wherein, in theinsulator-coated portion, each conductor has a circular section.
 7. Theelectric wire joint structure according to claim 3, wherein said slantface is disposed in a portion of said conductor which becomes thinnertoward the exposed portion, and is formed between the conductor in theinsulator-coated portion and the conductor in the exposed portion. 8.The electric wire joint structure according to claim 2, wherein; thesection of each conductor in the joined face portion has a rectangularshape defined by long sides and short sides; and the joining face ofeach conductor has an offset relative to the insulator coated portion ofsaid conductor, toward the joining face to which it is joined in thejoined face portion.
 9. The electric wire joint structure according toclaim 1, wherein: a slant face portion which becomes thinner toward theexposed conductor portion is formed between the conductor in theinsulator-coated portion and the conductor in the exposed conductorportion; a section of the conductor in the joined face portion has arectangular shape comprising long sides and short sides; and an outerend of the slant face portion on the long-sides' side extends up to aposition more distant from a tip of the exposed conductor portion thanan outer end portion of the slant face on the short sides' side.